Hydraulic cylinders are used, for example, in vehicles and in particular in construction machines such as excavators, wheel loaders and waist-or chassis-steered vehicles. According to the invention, in a preferred embodiment, a wheel loader is provided with two load arms, and at least one hydraulic cylinder that is designed to raise or lower the load arms in relation to the vehicle. There is a need with such an hydraulic cylinder to be able to deliver lubricant easily and efficiently to bearings arranged at the bearing point of the hydraulic cylinder on the load arm and on the vehicle in order to reduce wear in the bearing.
The use of time-controlled devices for delivering lubricant to such bearings is known. Such a time-controlled device delivers a predetermined quantity of lubricant to a bearing with a certain time interval. The time between each lubrication pulse is adjusted in order to deliver the quantity of lubricant needed in order to minimize the risk of wear in the bearing under the normal working load of the hydraulic cylinder.
One disadvantage with such a device is that lubricant is delivered to the bearing at each predetermined lubrication pulse regardless of the actual need for lubricant.
This means that under a high working load in the hydraulic cylinder, an insufficient quantity of lubricant is delivered to the bearing in relation to the actual need, which can lead to problems of wear and tear in the bearing.
Furthermore, at low working load in the hydraulic cylinder an excessive quantity of lubricant is delivered in relation to the actual need, which leads to problems of excess lubricant in the bearing.
Another disadvantage with such a device is that since lubricant is delivered when the bearing is under load, the lubricant will not be distributed right around the bearing. This is the case, in particular, in bearings with a small angle of rotation since there is a risk that a part of the bearing will never receive a sufficient quantity of lubricant.